The new role of TIPT on rejuvenation of water tree aged cables

In this paper, a new role of titanium isopropoxide (TIPT) catalyst is revealed on rejuvenation of water tree aged cables, and inorganic-TiO₂ particles are found in the water tree voids after rejuvenation. A water tree accelerated aging system with a needle electrode is used to obtain water trees in cross-linked polyethylene (XLPE) cable samples. By use of a scanning electron microscope (SEM), agglomerated nano-TiO₂ particles are found in the water tree areas of the injected samples. Furthermore, through analyzing the products of TIPT hydrolysis by using SEM and energy disperse spectroscopy (EDS), the nano-scale TiO₂ particles are observed. This proves that the hydrolysis reaction of TIPT can generate the TiO₂ particles. Breakdown voltage of samples directly injected TiO₂ particles and the rejuvenated samples are significantly higher than that of the aged samples and the new samples. Also, the TiO₂ particles are observed inside the breakdown channels of the rejuvenated samples. This indicates the TIPT can react with water in water tree and form the TiO₂ gel to fill water tree voids. Because of the filling effect of inorganic TiO₂ particles, the breakdown strength of the rejuvenated cables can be improved, which possibly suppresses the damage generated by the partial discharge inside the water tree.